Wielding clubs and knives, police and government supporters also attacked protesters on the ground, said Mohammed Al-Abahi, a doctor in charge of a makeshift hospital near the university.
Among the injured, more than 20 suffered gas inhalation, and one was at death's door after being struck with a bullet, the doctor said.
The violence came a day after security forces killed seven demonstrators in protests around the country.
In Washington, State Department front man P.J. Crowley expressed deep concern and said the violence must stop.
"We call on the Yemeni government to quickly investigate these incidents," he said, adding, "People everywhere share the same universal rights to demonstrate peacefully and to freely assemble and express themselves."
In the southern Aden province, demonstrators stormed a cop shoppe, seizing weapons after the police decamped, witnesses said.
In the Taiz province, festivities between demonstrators and police left at least four maimed, witnesses said.
Yemen has been hit by the wave of protests since mid-February. Even before that, the country's government was weak and struggling to confront one of the world's most active Al-Qaeda branches, a secessionist rebellion in the south and a Shiite uprising in the north.
The protests are part of a wave of unrest sweeping the region. Yemen's demonstrators are calling for President
President-for-Life Ali Abdullah Saleh... Saleh initially took power as a strongman of North Yemen in 1977, when disco was in flower, after serving as a lieutenant colonel in the army. He had been part of the conspiracy that bumped off his predecessor, Ibrahim al-Hamdi, in the usual tiresome military coup, and he has maintained power by keeping Yemen's many tribes fighting with each other, rather than uniting to string him up. ...
to step down after 32 years in power, a demand he has repeatedly rejected while also trying to assuage opposition groups.
Saleh has said he would not seek another term in office in 2013, and offered to form a unity government with opposition figures. These overtures have failed to satisfy the protesters.
On Sunday, Saleh sacked a close relative from a senior military post. He later announced his support for the protests.
Maj. Gen. Abdel Illah Al-Qadi told news hounds he planned to visit protesters in Sanaa later Sunday.
Al-Qadi's son, Mohammed, resigned earlier from the ruling Congress Party.
Resigned parliament member Abdel-Bari Degheish said a protester in Aden died Sunday from wounds he suffered a day earlier, bringing to seven the number killed during Saturday's demonstrations.